Question

A car travels 10 km in 20 minutes. If the speed remains the same, how far can it travel in 3 hours?
[2 marks]

Answer 1

Let, a car travels $x$ km in $3$ hours or $180$ minutes.
$\because 1hour=60$ minutes
$\therefore 3hour=60\times 3=180$ minutes

[0.5 mark]

Distance (in km)	$10$	$x$
Time (in minutes.)	$20$	$180$

As the time [T] will increases, distance [D] will also increase.
Hence, it is a case of direct proportion.
$\Rightarrow \frac{D}{T}=constant$
$\Rightarrow \frac{D_1}{T_1}=\frac{D_2}{T_2}$

[0.5 mark]

$\Rightarrow \frac{10}{20}=\frac{x}{180}$
$\Rightarrow x=\frac{10\times 180}{20}=90$

Hence, a car will cover a distance of $90$ km in $3$ hours or $180$ minutes.

[1 mark]